My Thought is you aren't MAKING someone love you...its not like they are being dragged kicking and screaming to love you, but rather you're harvesting feelings that are/have already been there. I don't think it's possible to make someone love you if they aren't capable of it on their own, in the same sense that you can't make yourself grow horns. In order to bend the energies of the universe there has to be something to work with..it has to be possible on some realm. Picking a stranger out of a crowd and performing rituals to make him have feelings for you that he never had is impossible. For this reason, I don't see love spells as going against the "will" of another, in a sense....there is already some sort of will there. Just my two cents, and perhaps I'm wrong, but that's my outlook.
I also agree with conjourdoc...aren't spells in general against the free will of everything, including the free will of the universe?